Honeycomb structural body and method of manufacturing honeycomb structural body

ABSTRACT

A honeycomb structural body includes multiple cores, at least face sheet, and at least one reinforcement sheet. The multiple cores each have a honeycomb structure, and are bonded to each other with foamed adhesive in a direction in which the number of multiple pores formed by the honeycomb structure increases. The at least one face sheet is adhered to the multiple cores so as to cover the multiple pores. The reinforcement sheet is placed between the multiple cores and the at least one face sheet, at a position where the reinforcement sheet covers the foamed adhesive.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2014-061870 filed on Mar. 25, 2014, the entire contents of which arehereby incorporated by reference.

BACKGROUND

1. Technical Field

An example of the present disclosure relates to a honeycomb structuralbody and a method of manufacturing the honeycomb structural body.

2. Related Art

Conventionally, honeycomb structural bodies are used as structuralmembers of airplanes in order to reduce weight and improve mechanicalstrength of the airplanes. For example, Japanese Unexamined PatentApplication Publication (JP-A) Nos. S60-097840, H10-006417, andH01-195024 disclose typical honeycomb structural bodies that are formedby sandwiching or laminating a core having a honeycomb structure withskins (face sheets) made of composite material, such as Fiber ReinforcedPlastics (FRP).

If the honeycomb structural body is large in size or has a curvedsurface, multiple cores having a honeycomb structure are preliminarilyjoined or bonded together. The preliminary bonding of the cores is oftencarried out with foamed adhesives that inflate by heat. Therefore, whenmanufacturing a large-sized honeycomb structural body, the cores arepreliminarily bonded by heat curing of the foamed adhesive, and skinprepreg(s) that is a material of the skin is then placed on the bondedcores. The laminated skin prepreg(s) and the bonded cores are heatedunder pressure.

SUMMARY OF THE INVENTION

A purpose of the present disclosure is to provide a honeycomb structuralbody that can be manufactured by simpler processes, and a method ofmanufacturing the honeycomb structural body.

An aspect of the present disclosure provides a honeycomb structural bodyincluding multiple cores that each have a honeycomb structure, and arebonded to each other with foamed adhesive in a direction in which thenumber of multiple pores formed by the honeycomb structure increases, atleast one face sheet adhered to the multiple cores so as to cover themultiple pores, and at least one reinforcement sheet placed betweenmultiple cores and the at least one face sheet, at a position where theat least one reinforcement sheet covers the foamed adhesive.

Another aspect of the present disclosure provides a method ofmanufacturing a honeycomb structural body including placing multiplecores that each have having a honeycomb structure on both sides offoamed adhesive in a direction in which the number of multiple poresformed by the honeycomb structure increases, placing at least one skinprepreg on the multiple cores so as to cover the multiple pores,protecting an outer surface side of the at least one skin prepreg by abagging film, at least one reinforcement sheets at least either one ofbetween the skin prepreg and the bagging film and between the at leastone skin prepreg and the multiple cores, at the position where the atleast one reinforcement sheet covers the foamed adhesive, andmanufacturing the honeycomb structural body in which the multiple coresare bonded to each other with the foamed adhesive and the at least oneface sheet that is cured is bonded to the multiple cores, by heating andpressurizing the multiple cores, the at least one skin prepreg, thebagging film, and the at least one reinforcement sheet in a set state.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example and not by wayof limitation in the figures of the accompanying drawings, in which thelike reference numerals indicate like elements and in which:

FIG. 1 is a cross-sectional view illustrating an example structure of ahoneycomb structural body according to a first example of the presentdisclosure;

FIG. 2 is a top view of the honeycomb structural body illustrated inFIG. 1;

FIG. 3 is a flowchart illustrating a method of manufacturing thehoneycomb structural body illustrated in FIG. 1;

FIG. 4 is a view illustrating the method of manufacturing the honeycombstructural body illustrated in FIG. 1;

FIG. 5 is a top view of the honeycomb structural body seen at a positionA-A of FIG. 4;

FIG. 6 is a cross-sectional view illustrating an example structure of ahoneycomb structural body and a method of manufacturing the honeycombstructural body, according to a second example of the presentdisclosure;

FIG. 7 is a flowchart illustrating the method of manufacturing thehoneycomb structural body illustrated in FIG. 6;

FIG. 8 is a top view illustrating an example structure of a honeycombstructural body according to a third example of the present disclosure;and

FIG. 9 is a cross-sectional view illustrating a method of manufacturingthe honeycomb structural body illustrated in FIG. 8, taken along a lineB-B.

FIG. 10 is an isolated view of a stack of reinforcement sheets, witheach reinforcement sheet in the stack having chamfers.

DETAILED DESCRIPTION

A honeycomb structural body and a method of manufacturing the honeycombstructural body according to several examples of the present disclosureare described with reference to the accompanying drawings.

First Example

FIG. 1 is a cross-sectional view illustrating an example structure of ahoneycomb structural body according to a first example of the presentdisclosure, and FIG. 2 is a top view of the honeycomb structural bodyillustrated in FIG. 1.

The honeycomb structural body 1 has a structure in which skins 3 areadhered on multiple cores 2. The cores 2 each has a honeycomb structure,and the cores 2 are bonded to each other with the foamed adhesive 4 in adirection in which the number of pores formed by the honeycombstructures increases. The honeycomb structure in which the core 2 has ina matrix is not limited to an angled cylindrical shape having ahexagonal shape in lateral cross section, but may be any othercylindrical shapes having any lateral cross-sectional shapes.

Further, the height of the honeycomb structure of each core 2 may beconstant, or may vary along a mold. In the example illustrated in FIGS.1 and 2, four corners of two bonded cores 2 incline.

The sheet-shaped skins 3 are adhered on the cores 2 so as to cover themultiple pores formed by the honeycomb structure. In the exampleillustrated in FIGS. 1 and 2, the cores 2 that is joined to each otherwith the foamed adhesive 4 is sandwiched by two sheets of skin 3. Thatis, the honeycomb structural body 1 has a sandwich structure in whichthe cores 2 is sandwiched by the two sheets of skin 3. In addition,since the four corners of the two cores 2 incline, the upper skin 3 alsoinclines along the cores 2.

Each skin 3 that constitutes the honeycomb structural body 1 is made ofcomposite material. On the other hand, the core 2 can be made ofcomposite material or metal.

The honeycomb structural body 1 having such a structure can be used as astructural component of, for example, an airplane. That is, the skins 3and the cores 2 can constitute components of the airplane.

Next, a method of manufacturing the honeycomb structural body 1 isdescribed.

FIG. 3 is a flowchart illustrating the method of manufacturing thehoneycomb structural body 1 illustrated in FIG. 1. FIG. 4 is a viewillustrating the method of manufacturing the honeycomb structural body 1illustrated in FIG. 1, and FIG. 5 is a top view of the honeycombstructural body 1 seen at a position A-A of FIG. 4.

In Step S1, a skin prepreg 10L that is the material of the lower skin 3is first placed on a molding jig T. Next, at Step S2, the cores 2 eachhaving the honeycomb structure is placed on the lower skin prepreg 10L.Note that the cores 2 is disposed on both sides of the foamed adhesive 4in the direction in which the number of multiple pores formed by thehoneycomb structure increases. Next, at Step S3, a skin prepreg 10U thatis the material of the upper skin 3 is placed on the cores 2 so as tocover the multiple pores formed by the honeycomb structure.

Next, at Step S4, a reinforcement sheet R is disposed on the outersurface side of the upper skin prepreg 10U as part of the molding jig T,at such a position that the reinforcement sheet R covers the foamedadhesive 4. Next, at Step S5, the outer surface side of the upper skinprepreg 10U where the reinforcement sheet R is disposed is protected bya film-shaped bagging film 11. Next, at Step S6, an internal spaceprotected by the bagging film 11 is evacuated. As a result, asemi-finished product of the honeycomb structural body 1 comprised ofthe lower skin prepreg 10L, the cores 2, the foamed adhesive 4, and theupper skin prepreg 10U is pressurized together with the reinforcementsheet R by atmospheric pressure.

Next, at Step S7, the semi-finished product of the honeycomb structuralbody 1 and the reinforcement sheet R that are pressurized by evacuatingthe internal space of the bagging film 11 are transferred into anautoclave apparatus. Then, the foamed adhesive 4 and the upper and lowerskin prepregs 10U and 10L are thermally cured by autoclave processing.As a result, the honeycomb structural body 1 in which the upper skin 3and the lower skin 3 are bonded to the cores 2 bonded with the foamedadhesive 4 can be obtained so that the upper and lower skins 3 aredeformed into predetermined shapes.

As described above, because the cores 2, the skin prepregs 10U and 10L,the bagging film 11, and the reinforcement sheet R are heated andpressurized in a set state, the honeycomb structural body 1 in which thecores 2 is bonded to each other with the foamed adhesive 4, and thecured skins 3 are bonded to the cores 2, can be manufactured.

That is, since the reinforcement sheet R is disposed at the positionbetween the bagging film 11 and the skin prepreg 10U where thereinforcement sheet R covers the foamed adhesive 4, the adhesion of thecores 2 with the foamed adhesive 4 and the curing of the skin prepregs10U and 10L can be performed by the single heating process. This is madepossible by the upper skin prepreg 10U not being dented because part ofthe upper skin prepreg 10U placed over the foamed adhesive 4 ismechanically reinforced by the reinforcement sheet R when the upper skinprepreg 10U is heated and pressurized.

In other words, if the adhesion of the cores 2 with the foamed adhesive4 and the curing of the skin prepregs 10U and 10L are performed in asingle heating process without providing the reinforcement sheet R, thepart of the upper skin prepreg 10U placed over the foamed adhesive 4will be distorted. As a result, the honeycomb structural body 1 isdeteriorated in its appearance and mechanical strength, resulting indifficulties to satisfy quality requirements of the product. For thisreason, it has been considered to be unreal to perform the adhesion ofthe cores 2 with the foamed adhesive 4 and the curing of the skinprepregs 10U and 10L in a single heating process.

On the other hand, if the honeycomb structural body 1 is manufactured bythe manufacturing method described above, the honeycomb structural body1 having the satisfactory appearance and mechanical strength can bemanufactured at least in a single heating process.

It is preferred to provide multiple reinforcement sheets R between theupper skin prepreg 10U and the bagging film 11 as illustrated in FIGS. 4and 5 in order to prevent the deterioration of quality, such as the dentand damages of the upper skin prepreg 10U. If the reinforcement sheets Ris provided between the upper skin prepreg 10U and the bagging film 11,the reinforcement sheets R having mutually different widths asillustrated can be placed so that the reinforcement sheets R forms stepsin thickness directions thereof.

In particular, if the reinforcement sheets R having flexibility islaminated in the stepped manner, flexibility can be maintained whilesecuring the thickness that can bear the forming pressure. Therefore,even if the ideal post-cured shape of the skin 3 involves a complicatedcurved surface, the reinforcement sheets R can be bent along the skin 3.

In addition, it is effective for each reinforcement sheet R to formchamfers to conform to the post-cured shape of the skin 3.

Damages to the skin 3 due to the placement of the reinforcement sheets Rcan be avoided by adjusting the widths of the reinforcement sheets R andforming the chamfers and, thus, the ideal post-fabricated shape of theskin 3 can be obtained. That is, the mechanical strength of thereinforcement sheets R that is enough to prevent the dent of the skinprepreg 10U can be secured, without forming the steps at the edges ofthe reinforcement sheets R that may cause the damages to the skin 3and/or insufficient deformation of the skin 3.

Cured prepreg is suitable for the material of the reinforcement sheet R.In particular, it was confirmed to be effective for preventing the dentof the skin prepreg 10U from the results of examinations, if thereinforcement sheet R1 comprised of GFRP (Glass Fiber ReinforcedPlastics) is disposed on the skin prepreg 10U side, and thereinforcement sheet R2 comprised of CFRP (Carbon Fiber ReinforcedPlastics) on the bagging film 11 side.

This is considered to be made possible because the conformity of thereinforcement sheet R1 to the shape of the skin prepreg 10U is improvedby disposing the reinforcement sheet R1 comprised of the flexible GFRPon the skin prepreg 10U side. Note that the reinforcement sheet R1comprised of GFRP may be adhered to the skin prepreg 10U by usingTeflon® tape 12 as needed.

That is, the honeycomb structural body 1 described above is manufacturedin a single thermal curing process by providing the reinforcement sheetR between the upper skin prepreg 10U and the bagging film 11, althoughthe curing of prepreg and the adhesion of the cores 2 are required.Further, the method of manufacturing the honeycomb structural body 1enables the honeycomb structural body 1 to be manufactured in a singlethermal curing process by providing the reinforcement sheet R betweenthe upper skin prepreg 10U and the bagging film 11, although the curingof prepreg and the adhesion of the cores 2 are required.

Effects of the Invention

As described above, according to the method of manufacturing thehoneycomb structural body 1, the honeycomb structural body 1 can bemanufactured by simpler processes. That is, the preliminary bonding ofthe honeycomb cores that has been conventionally necessary becomesunnecessary, and the bonding of the cores 2 and the curing of the skinprepregs 10U and 10L can be simultaneously achieved in a single heatingprocess.

If the preliminary bonding of the honeycomb cores is performed usingadhesives that harden at room temperature, sufficient adhesive strengthwill not be obtained. On the other hand, if the bonding of the honeycombcores and the curing of skin prepregs are performed simultaneously withthe foamed adhesive, there has been a problem that a local dent isproduced from the gap as the starting point in the bonding part of thehoneycomb cores due to the pressurizing by evacuation or formation ofthe skin prepregs. Therefore, in order to avoid the poor appearance andthe lack of strength, the heating and pressurizing have beenconventionally required for the preliminary bonding of the honeycombcores using the foamed adhesive prior to the heating for curing the skinprepregs.

On the other hand, according to the method of manufacturing thehoneycomb structural body 1, the dent of the skin prepreg 10U can beprevented by providing the reinforcement sheet R between the skinprepreg 10U and the bagging film 11. As a result, the preliminarybonding of the cores 2 becomes unnecessary, and the honeycomb structuralbody 1 can be manufactured in a single heating process. Therefore, themanufacturing cost of the honeycomb structural body 1 can be reduced.

In addition, if the preliminary bonding of the honeycomb cores isperformed, the trace of the preliminary bonding of the honeycomb coresremains, but the trace of the preliminary bonding does not remain in thehoneycomb structural body 1. Therefore, the honeycomb structural body 1of higher quality in appearance than the conventional technique can bemanufactured.

Second Example

FIG. 6 is a cross-sectional view illustrating an example structure of ahoneycomb structural body and a method of manufacturing the honeycombstructural body according to a second example of the present disclosure.

A honeycomb structural body 1A of the second example illustrated in FIG.6 is different from the honeycomb structural body 1 of the first examplein that the reinforcement sheet 20 is disposed between the cores 2 andthe skin 3, at the position where the reinforcement sheet 20 covers thefoamed adhesive 4. Since other configurations and operations of thehoneycomb structural body 1A of the second example do not substantiallydiffer from the honeycomb structural body 1 of the first example, thesame configurations are denoted by the same reference numerals anddescription thereof is omitted.

In the honeycomb structural body 1A, the reinforcement sheet 20 isdisposed between the cores 2 and the skin 3, as a constituent element.The reinforcement sheet 20 is adhered to at least either one of thecores 2 or the skin 3 with film adhesive 21, as needed.

The reinforcement sheet 20 provided between the cores 2 and the skin 3is appropriately made of composite material. Further, it is desirable toform chamfers that conform to the shape of the skin 3, in thereinforcement sheet 20 provided between the cores 2 and the skin 3.Next, the method of manufacturing the honeycomb structural body 1A isdescribed.

FIG. 7 is a flowchart illustrating the method of manufacturing thehoneycomb structural body 1A illustrated in FIG. 6. Note that similarsteps to those of the flowchart illustrated in FIG. 3 are denoted withthe same reference numerals, and description thereof is omitted.

When manufacturing the honeycomb structural body 1A having thereinforcement sheet 20 between the cores 2 and the skin 3, thereinforcement sheet 20 is placed at Step S10 before placing the upperskin prepreg 10U. The reinforcement sheet 20 is placed between the upperskin prepreg 10U and the cores 2, at the position where thereinforcement sheet 20 covers the foamed adhesive 4, as illustrated inFIG. 6.

The reinforcement sheet 20 can be adhered to at least either one of thecores 2 or the upper skin prepreg 10U with the film adhesive 21.

The material of reinforcement sheet 20 is appropriately made of a sheetprepreg cured in advance. Thus, the honeycomb structural body 1A havingthe reinforcement sheet 20 comprised of composite material between thecores 2 and the skin 3 can be manufactured by heating and pressurizing asemi-finished product of the honeycomb structural body 1A containing thelower skin prepreg 10L, the cores 2, the foamed adhesive 4, thereinforcement sheet 20 comprised of the prepreg cured in advance, andthe upper skin prepreg 10U.

Such a honeycomb structural body 1A of the second example ismanufactured by thermally curing in a state where the reinforcementsheet 20 is placed between the upper skin prepreg 10U and the cores 2,in addition to the reinforcement sheet R placed between the upper skinprepreg 10U and the bagging film 11. Thus, like a case where the gapsbetween the cores 2 are large, or a case where the pore diameter of thehoneycomb structure is large, the generation of the dent can beprevented more certainly even if it is in a condition in which the dentstend to be easily generated between the cores 2.

In particular, as illustrated in FIG. 6, it was confirmed byexaminations to be effective to place the first reinforcement sheet 20made of the cured prepreg between the skin prepreg 10U and the cores 2,the second reinforcement sheet R3 made of GFRP on the skin prepreg 10Uside between the skin prepreg 10U and the bagging film 11, and the thirdreinforcement sheet R4 made of CFRP to the bagging film 11 between theskin prepreg 10U and the bagging film 11, respectively. In addition, itwas confirmed to be effective to use FRP having flexibility as the firstreinforcement sheet 20.

Third Example

FIG. 8 is a top view illustrating an example structure of a honeycombstructural body according to a third example of the present disclosure,and FIG. 9 is a cross-sectional view illustrating a method ofmanufacturing the honeycomb structural body illustrated in FIG. 8, takenalong a line B-B.

The honeycomb structural body 1B of the third example illustrated inFIG. 8 is different from the honeycomb structural bodies 1 and 1A of thefirst and second examples in that the cores 2 is externally exposed.Since other configurations and operations of the honeycomb structuralbody 1B of the third example do not substantially differ from thehoneycomb structural bodies 1 and 1A of the first and second examples,the same configurations are denoted by the same reference numerals anddescription thereof is omitted.

As illustrated in FIG. 8, the honeycomb structural body 1B, in which theentire surface of the cores 2 having honeycomb structures is not closedor covered by the skin 3, may also be manufactured. In the exampleillustrated in FIG. 8, the cores 2 are externally exposed at four sidefaces of the honeycomb structural body 1B. In such a case, one or morestoppers 30 for preventing a slip of the cores 2 may be provided atnecessary locations as jigs, as illustrated in FIG. 9.

The reinforcement sheet of this example is similarly placed to the firstand second examples. Note that, if the reinforcement sheet 20 isprovided between the skin prepreg 10U and the cores 2, the reinforcementsheet R to be placed between the bagging film 11 and the skin prepreg10U may be omitted. That is, the honeycomb structural body 1B can bemanufactured by placing the reinforcement sheets R and 20 at leasteither one of between the skin prepreg 10U and the bagging film 11 orbetween the skin prepreg 10U and the cores 2, at the position where thereinforcement sheets R and 20 cover the foamed adhesive 4.

Other Examples

As described above, although particular examples of the presentdisclosure are described, these examples are merely examples and do notlimit the scope of the present disclosure. The novel method and devicedescribed herein may be embodied in other various forms. Further, theforms of the method and device described herein may be variouslyomitted, substituted and changed or modified without departing from thescope of the present disclosure. The appended claims and theirequivalents encompass such various forms and modifications as beingfallen under the scope and the spirit of the present disclosure.

The invention claimed is:
 1. A method of manufacturing a honeycombstructural body, comprising; placing multiple cores that each have ahoneycomb structure on both sides of foamed adhesive in a direction inwhich a number of multiple pores formed by the honeycomb structure isincreased; placing at least one skin prepreg on the multiple cores so asto cover the multiple pores; protecting an outer surface side of the atleast one skin prepreg by a bagging film; placing at least onereinforcement sheet between the at least one skin prepreg and themultiple cores at a position where the at least one reinforcement sheetcovers the foamed adhesive; and manufacturing the honeycomb structuralbody in which the multiple cores are bonded to each other with thefoamed adhesive, and the at least one skin prepreg is cured and bondedto the multiple cores, by heating and pressurizing the multiple cores,the at least one skin prepreg, the bagging film, and the at least onereinforcement sheet in a set state, wherein a pre-cured prepreg is usedas the at least one reinforcement sheet.
 2. The method of manufacturingthe honeycomb structural body of claim 1, further comprising: placing astack of reinforcement sheets between the at least one skin prepreg andthe bagging film, wherein the stack of reinforcement sheets comprisessheets that have mutually different widths and which are placed betweenthe at least one skin prepreg and the bagging film in order of width. 3.The method of manufacturing the honeycomb structural body of claim 2,wherein the stack of reinforcement sheets placed between the at leastone skin prepreg and the bagging film comprises a reinforcement sheetmade of glass fiber reinforced plastics that is placed on the at leastone skin prepreg side between the at least one skin prepreg and thebagging film, and a reinforcement sheet made of carbon fiber reinforcedplastics that is placed on the bagging film side between the at leastone skin prepreg and the bagging film.
 4. The method of manufacturingthe honeycomb structural body of claim 2, wherein the at least onereinforcement sheet placed between the at least one skin prepreg and themultiple cores is bonded with a film adhesive to the multiple cores, theat least one skin prepreg, or both the multiple cores and the at leastone skin prepreg.
 5. The method of manufacturing the honeycombstructural body of claim 1, further comprising: placing a stack ofreinforcement sheets between the at least one skin prepreg and thebagging film, wherein the stack of reinforcement sheets comprises areinforcement sheet made of glass fiber reinforced plastics that isplaced on the at least one skin prepreg side between the at least oneskin prepreg and the bagging film, and a reinforcement sheet made ofcarbon fiber reinforced plastics that is placed on the bagging film sidebetween the at least one skin prepreg and the bagging film.
 6. Themethod of manufacturing the honeycomb structural body of claim 5,wherein the at least one reinforcement sheet placed between the at leastone skin prepreg and the multiple cores is bonded with a film adhesiveto the multiple cores, the at least one skin prepreg, or both themultiple cores and the at least one skin prepreg.
 7. The method ofmanufacturing the honeycomb structural body of claim 1, wherein the atleast one reinforcement sheet is bonded with a film adhesive to themultiple cores, the at least one skin prepreg, or both the multiplecores and the at least one skin prepreg.
 8. A method of manufacturing ahoneycomb structural body, comprising: placing multiple cores that eachhave a honeycomb structure on both sides of foamed adhesive in adirection in which a number of multiple pores formed by the honeycombstructure is increased; placing at least one skin prepreg on themultiple cores so as to cover the multiple pores; protecting an outersurface side of the at least one skin prepreg by a bagging film; placingat least one reinforcement sheet at, at least, either one of between theat least one skin prepreg and the bagging film, and between the at leastone skin prepreg and the multiple cores, at a position where the atleast one reinforcement sheet covers the foamed adhesive; andmanufacturing the honeycomb structural body in which the multiple coresare bonded to each other with the foamed adhesive, and the at least oneskin prepreg is cured and bonded to the multiple cores, by heating andpressurizing the multiple cores, the at least one skin prepreg, thebagging film, and the at least one reinforcement sheet in a set state,wherein the at least one reinforcement sheet comprises multiplereinforcement sheets including a first reinforcement sheet made of curedprepreg that is placed between the at least one skin prepreg and themultiple cores, a second reinforcement sheet made of glass fiberreinforced plastics that is placed on the at least one skin prepreg sidebetween the at least one skin prepreg and the bagging film, and a thirdreinforcement sheet made of carbon fiber reinforced plastics that isplaced on the bagging film side between the at least one skin prepregand the bagging film.
 9. The method of manufacturing the honeycombstructural body of claim 8, wherein the at least one reinforcement sheetplaced between the at least one skin prepreg and the multiple cores isbonded with a film adhesive to the multiple cores, the at least one skinprepreg, or both the multiple cores and the at least one skin prepreg.10. A method of manufacturing a honeycomb structural body, comprising:placing multiple cores that each have a honeycomb structure on bothsides of foamed adhesive in a direction in which a number of multiplepores formed by the honeycomb structure is increased; placing at leastone skin prepreg on the multiple cores so as to cover the multiplepores; protecting an outer surface side of the at least one skin prepregby a bagging film; placing at least one reinforcement sheet at, atleast, either one of between the at least one skin prepreg and thebagging film, and between the at least one skin prepreg and the multiplecores, at a position where the at least one reinforcement sheet coversthe foamed adhesive; and manufacturing the honeycomb structural body inwhich the multiple cores are bonded to each other with the foamedadhesive, and the at least one skin prepreg is cured and bonded to themultiple cores, by heating and pressurizing the multiple cores, the atleast one skin prepreg, the bagging film, and the at least onereinforcement sheet in a set state, wherein the at least onereinforcement sheet comprises multiple reinforcement sheets including areinforcement sheet made of cured prepreg that is placed between the atleast one skin prepreg and the multiple cores, and a stack ofreinforcement sheets that have mutually different widths and are placedbetween the at least one skin prepreg and the bagging film in order ofthe width, the stack of reinforcement sheets comprising a reinforcementsheet made of glass fiber reinforced plastics that is placed on the atleast one skin prepreg side between the at least one skin prepreg andthe bagging film, and a reinforcement sheet made of carbon fiberreinforced plastics that is placed on the bagging film side between theat least one skin prepreg and the bagging film.
 11. The method ofmanufacturing the honeycomb structural body of claim 10, wherein the atleast one reinforcement placed between the at least one skin prepreg andthe multiple cores is bonded with a film adhesive to the multiple cores,the at least one skin prepreg, or both the multiple cores and the atleast one skin prepreg.